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Biomedical subjects

P Landry

Publications and source records attributed to P Landry.

At least 19 recordsLinked to original sources
PubMed1998

[Comparative immunogenicity of 2 antirabies vaccines in a 2-1-1 post-exposure vaccination schedule].

Few trials have compared the Purified Duck Embryo Vaccine (PDEV) and the Human Diploid Cell Vaccine (HDCV) in a post-exposure immunization schedule of 4 shots (2 on day 0 and 1 each on day 7 and 21, or 2-1-1 schedule). A retrospective analysis compared 10 patients with PEDV and 20 with HDCV, who had received the 2-1-1 schedule as well as 20 UI mg/kg of immune globulins on day 0. The median neutralizing antibody titers on day 21 (after 3 doses) and the median of maximum titers until day 90 were higher for HDCV than for PEDV (0.6 IU/ml versus 3.5 IU/ml [p < 0.04] and 2.5 IU/ml versus 5.8 IU/ml [p < 0.03] respectively). Seven patients had not reached the seroconversion titer of 0.5 IU/ml after 3 doses (day 21). These results differ from previous studies showing a 100% seroconversion rate on day 21, and suggest that more studies are required before these 2 vaccines can be used in the 2-1-1 schedule after severe exposure.

Adult↗
PubMed1998

[The value of screening serology in anti-hepatitis A vaccination of travelers].

UNLABELLED: To select the travellers most likely to benefit from anti-hepatitis A (HA) antibody testing, the following criteria have been proposed: (A) being born before 1945, (B) a stay over 1 year in a developing country or (C) a history of jaundice. We present a prospective study to assess the practical use of these criteria. Following a recent survey in the general population of Lausanne showing HA seroprevalence of 52.6% in the age group over 45, we included an A1 criterion (A extended to birth before 1950). Anti-HA IgG testing and a questionnaire were proposed to all travellers presenting one or more criteria. RESULTS: Out of 1187 consecutive travellers, 176 (14.8%) had one or more criteria (219 [18.5%] when A1 was used). Criteria A applied to 8.5% of all travellers, A1 to 13.8%, B to 6.3% and C to 3.1%. Only 3% of travellers had more than one criterion. Overall seroprevalence among the selected group was 48.3%. Seroprevalence of travellers below 60 years old was under 30%, unless a second criterion was present in which case seroprevalence was 10% higher. Eighty percent of travellers with a history of jaundice were found to be positive. The use of the recommended criteria spared 94 travellers (46.3% of those tested and 7.9% of all travellers) unnecessary immunisation. Among travellers older than 60 years, a 30% economy on the total sum for immunising all of them, without any prior testing was realised. CONCLUSIONS: Among the population of travelers consulting our travel clinic, the seroprevalence for HA is lower than in the general population. We recommend that testing should be proposed only to travellers aged over 60, or with a history of jaundice, or to those with a combination of 2 out of 3 criteria.

Adult↗
PubMed1997

[Routine cases in intestinal parasitology].

The majority of intestinal parasites isolated in Switzerland is imported by refugees and travellers. Nematodes are more frequently isolated in the first group, whereas Giardia duodenalis and Strongyloides stercoralis predominate in the second. Symptoms are usually mild, but occasionally diarrhea, abdominal pain and weight loss may be encountered. Hypereosinophilia occurs frequently with some parasites. Four cases chosen from the outpatient department of a Swiss medical polyclinic are presented and serve as a basis for discussing persistent and chronic diarrhea, acute traveller's diarrhea, and hypereosinophilia. Differential diagnosis according to type and duration of symptoms, laboratory findings and treatment of the most frequently encountered parasites are reviewed.

Adult↗
PubMed1997

Apoptosis is coordinately regulated with osteoblast formation during bone healing.

The ultimate fate of the expanded pool of osteoblasts formed following a typical bone injury is unclear. Since necrosis has not been described in the latter stages of bone healing, there must be some other mechanism by which obsolete osteoblasts are cleared from an injury site. We therefore evaluated the possibility that their removal is pre-programmed, by investigating the occurrence of apoptosis in rats that received a standardized bone injury. Histological evidence identical to that found in tissues known to exhibit apoptosis was obtained, thereby showing that programmed cell death was a normal concomitant of fracture healing. The concentration of apoptotic bodies reached its maximum after the differentiative response had peaked, suggesting that the two processes were coordinated. The same result was found in a second group of rats that received the same bone injury plus a simultaneous standardized soft-tissue injury. The combined injuries resulted in more osteoblasts and more apoptotic bodies, but an identical temporal relationship between the peak responses in the two parameters. The results suggested that osteoblasts were removed from the injury site via apoptosis, and that the process was coordinately regulated with differentiation. Since the number of apoptotic bodies per osteoblast varied during healing, it is likely that apoptosis was associated with healing and not merely with osteoblast concentration.

Animals↗
PubMed1988

Somatosensory cortical neurons with an identifiable electrophysiological signature.

In both cats and rats, neurons with a distinctively narrow action potential were recognized as a small subset of all neurons isolated in the somatosensory cortex. These cells were characterized by generally having a spontaneous activity, some evidence of an afferent input, a sensitivity to glutamate but a relative resistance to depolarization block induced by glutamate and a marked insensitivity to acetylcholine. Two were filled with horseradish peroxidase (HRP) and recovered. Although others have suggested that such neurons are interneurons, following reconstruction it was apparent that the two cells filled with HRP were pyramidal cells. These observations suggest that there may be more than one class of cortical neurons with thin spikes.

Action Potentials↗
PubMed1987

Morphological and electrophysiological characteristics of somatosensory thalamocortical axons studied with intra-axonal staining and recording in the cat.

The intracortical arborizations of thalamocortical fibers arising from the ventroposterolateral (VPL) nucleus in the cat were studied following intra-axonal injections of horseradish peroxidase (HRP). The axons were impaled 1.5 to 3 mm below the surface of the cortex, identified electrophysiologically by stimulating the VPL nucleus and functionally by stimulating the somatic receptive field with natural stimuli. Many of the results obtained in a previous study using similar techniques (Landry and Deschênes 1981) were confirmed by the present experiments. Fibers activated by cutaneous stimulation arborized either in area 3b or 1 but some did send branches to both areas. Also, the intracortical arborization of a rapidly adapting cutaneous afferent fiber in area 2 is described. The size and tangential extent of the fiber in area 2 are similar to those arborizing in other areas of the primary somatosensory cortex and consist of multiple patches separated by uninvaded gaps. One fiber activated by stimulation of deep tissue receptors gave rise to two bushes that arborized along a rostrocaudal axis exclusively in area 3b. Terminal boutons and varicosities were found mostly in layers VI, IV, the bottom third of III and the upper portion of V, but some fibers did send a few collateral branches to layer II and the bottom part of layer I. The results suggest that in the forebrain representation, the same modality and submodality can be recorded in more that one cytoarchitectonic area but that areas 3b, 1 and 2 should not be considered as a single functionally homogeneous area. Counts of terminals suggest that a single fiber arborizing in area 1 makes as many as 3 times the number of synapses made in area 2 or 3b. Since fibers appear to be modality and submodality specific, if convergence of modality, submodality and/or body areas occur in the cortex, then this must be preferentially, but not exclusively, done by thalamic fibers of different functions which arborize in the same cytoarchitectonic area and synapse upon a shared postsynaptic target. In the same experiments intra-axonal recordings revealed the presence of two hyperpolarizing after potentials elicited by a preceding action potential. The first after potential was associated with a decrease in excitability of the fiber and an increase in membrane resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1986

Bicuculline-induced alterations of response properties in functionally identified ventroposterior thalamic neurones.

Extracellular recordings of 105 neurones in the cat's somatosensory thalamus were obtained with carbon fibre-containing multibarrel micropipettes. The responses of cells to natural stimulation of cutaneous or deep structures were characterized and the responses to electrical stimulation of primary somatosensory cortex were determined. Receptive fields were mapped and the functional properties were examined before and during the microiontophoretic administration of glutamate, gamma-aminobutyric acid (GABA) and bicuculline methiodide (BMI). Modality and submodality properties of all cells tested apparently remained unchanged qualitatively, despite all pharmacological interventions. BMI lowered the response threshold of a majority of the 48 cells tested for this variable, although almost 25% responded with elevated thresholds. BMI changed the temporal properties of the responses of both thalamocortical relay neurones and of presumed interneurones. Discharges evoked by natural stimuli and by electrical stimulation of the cortex were prolonged and their pattern was altered. Decreases in the frequency of bursts of discharges were often observed with BMI, and these bursts were invariably prolonged and the interspike interval profiles were altered. Receptive field size changes were observed only in 8 of 48 neurones. For two of these, the field size decreased, while for the others there were small increases.

Action Potentials↗
PubMed1985

Identification of two populations of corticothalamic neurons in cat primary somatosensory cortex.

Extracellular and intracellular recordings of corticothalamic (CT) cells were performed in the primary somatosensory cortex of the cat. CT neurons were antidromically activated by electrically stimulating the ventroposterior lateral (VPL) nucleus of the thalamus and were classified into two types according to their physiological properties. Type 1 had no spontaneous activity and no identifiable somatic receptive field. Type 2 fired action potentials spontaneously and responded to mechanical stimulation of the skin or underlying tissues. Axonal conduction velocities were slower for type 1 cells and their cell bodies were located slightly deeper in the cortex than those of type 2 cells. Both types of CT neurons exhibited inhibitory postsynaptic potentials in response to VPL stimulation but an early synaptic excitation and rebound discharge was observed almost exclusively in type 2 cells. These results suggest that only type 2 CT cells can modify the activity of thalamic neurons through a corticothalamic feedback loop.

Action Potentials↗